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  <div class="section" id="hello-world-http-client">
<span id="id1"></span><h1>&#8220;Hello world&#8221; HTTP client<a class="headerlink" href="#hello-world-http-client" title="Permalink to this headline">¶</a></h1>
<p>Since we have a &#8220;Hello World&#8221; HTTP server, let&#8217;s then create an HTTP client to
access that server. This client will be similar to the HTTP client we made
earlier in the documentation.</p>
<div class="section" id="the-code">
<h2>The code<a class="headerlink" href="#the-code" title="Permalink to this headline">¶</a></h2>
<p>We want to create a simple HTTP client that just makes a request to the HTTP
server that we created earlier. This really simple client will look like this:</p>
<div class="highlight-c++"><div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&lt;boost/network/protocol/http/client.hpp&gt;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&lt;string&gt;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&lt;sstream&gt;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&lt;iostream&gt;</span><span class="cp"></span>

<span class="k">namespace</span> <span class="n">http</span> <span class="o">=</span> <span class="n">boost</span><span class="o">::</span><span class="n">network</span><span class="o">::</span><span class="n">http</span><span class="p">;</span>

<span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span> <span class="n">argv</span><span class="p">[])</span> <span class="p">{</span>
    <span class="k">if</span> <span class="p">(</span><span class="n">argc</span> <span class="o">!=</span> <span class="mi">3</span><span class="p">)</span> <span class="p">{</span>
        <span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Usage: &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">argv</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; address port&quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
        <span class="k">return</span> <span class="mi">1</span><span class="p">;</span>
    <span class="p">}</span>

    <span class="k">try</span> <span class="p">{</span>
        <span class="n">http</span><span class="o">::</span><span class="n">client</span> <span class="n">client</span><span class="p">;</span>
        <span class="n">std</span><span class="o">::</span><span class="n">ostringstream</span> <span class="n">url</span><span class="p">;</span>
        <span class="n">url</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;http://&quot;</span> <span class="o">&lt;&lt;</span> <span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;:&quot;</span> <span class="o">&lt;&lt;</span> <span class="n">argv</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;/&quot;</span><span class="p">;</span>
        <span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">request</span> <span class="n">request</span><span class="p">(</span><span class="n">url</span><span class="p">.</span><span class="n">str</span><span class="p">());</span>
        <span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">response</span> <span class="n">response</span> <span class="o">=</span>
            <span class="n">client</span><span class="p">.</span><span class="n">get</span><span class="p">(</span><span class="n">request</span><span class="p">);</span>
        <span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="n">body</span><span class="p">(</span><span class="n">response</span><span class="p">)</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
    <span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">exception</span> <span class="o">&amp;</span> <span class="n">e</span><span class="p">)</span> <span class="p">{</span>
        <span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="n">e</span><span class="p">.</span><span class="n">what</span><span class="p">()</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
        <span class="k">return</span> <span class="mi">1</span><span class="p">;</span>
    <span class="p">}</span>
    <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="building-and-running-the-client">
<h2>Building and running the client<a class="headerlink" href="#building-and-running-the-client" title="Permalink to this headline">¶</a></h2>
<p>Just like with the HTTP Server and HTTP client example before, we can build this
example by doing the following on the shell:</p>
<div class="highlight-bash"><div class="highlight"><pre><span></span>$ <span class="nb">cd</span> ~/cpp-netlib-build
$ make hello_world_client
</pre></div>
</div>
<p>This example can be run from the command line as follows:</p>
<div class="highlight-bash"><div class="highlight"><pre><span></span>$ ./example/hello_world_client http://127.0.0.1:8000
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">This assumes that you have the <code class="docutils literal"><span class="pre">hello_world_server</span></code> running on
localhost port 8000.</p>
</div>
</div>
<div class="section" id="diving-into-the-code">
<h2>Diving into the code<a class="headerlink" href="#diving-into-the-code" title="Permalink to this headline">¶</a></h2>
<p>All this example shows is how easy it is to write an HTTP client that connects
to an HTTP server, and gets the body of the response. The relevant lines are:</p>
<div class="highlight-c++"><div class="highlight"><pre><span></span><span class="n">http</span><span class="o">::</span><span class="n">client</span> <span class="n">client</span><span class="p">;</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">request</span> <span class="n">request</span><span class="p">(</span><span class="n">url</span><span class="p">.</span><span class="n">str</span><span class="p">());</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">response</span> <span class="n">response</span> <span class="o">=</span>
    <span class="n">client</span><span class="p">.</span><span class="n">get</span><span class="p">(</span><span class="n">request</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="n">body</span><span class="p">(</span><span class="n">response</span><span class="p">)</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
</pre></div>
</div>
<p>You can then imagine using this in an XML-RPC client, where you can craft the
XML-RPC request as payload which you can pass as the body to a request, then
perform the request via HTTP:</p>
<div class="highlight-c++"><div class="highlight"><pre><span></span><span class="n">http</span><span class="o">::</span><span class="n">client</span> <span class="n">client</span><span class="p">;</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">request</span> <span class="n">request</span><span class="p">(</span><span class="s">&quot;http://my.webservice.com/&quot;</span><span class="p">);</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">response</span> <span class="o">=</span>
    <span class="n">client</span><span class="p">.</span><span class="n">post</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="n">some_xml_string</span><span class="p">,</span> <span class="s">&quot;application/xml&quot;</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">data</span> <span class="o">=</span> <span class="n">body</span><span class="p">(</span><span class="n">response</span><span class="p">);</span>
</pre></div>
</div>
<p>The next set of examples show some more practical applications using
the <code class="xref py py-mod docutils literal"><span class="pre">cpp-netlib</span></code> HTTP client.</p>
</div>
</div>


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  <h3><a href="../../contents.html">Table Of Contents</a></h3>
  <ul>
<li><a class="reference internal" href="#">&#8220;Hello world&#8221; HTTP client</a><ul>
<li><a class="reference internal" href="#the-code">The code</a></li>
<li><a class="reference internal" href="#building-and-running-the-client">Building and running the client</a></li>
<li><a class="reference internal" href="#diving-into-the-code">Diving into the code</a></li>
</ul>
</li>
</ul>

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